Response surface methodology was used to investigate the effect and interactions of processing variablessuch as roselle extract (0.1–1.3%), soybean oil (5–20%) on physicochemical, textural and sensory propertiesof cooked pork patties. It was found that reduction in thickness, pH, L* and b* values decreased; however,water-holding capacity, reduction in diameter and a* values increased, respectively, as the amount of roselleincreased. Soybean oil addition increased water-holding capacity, reduction in thickness, b* values of the pat-ties. The hardness depended on the roselle and soybean oil added, as its linear effect was negative at pb0.01.The preference of color, tenderness, juiciness, and overall quality depend on the addition of roselle and soy-bean oil. The maximum overall quality score (5.42) was observed when 12.5 g of soybean oil and 0.7 g of ro-selle extract was added. The results of this optimization study would be useful for meat industry that tends toincrease the product yield for patties using the optimum levels of ingredients by RSM.
Hibiscus sabdariffa L. (family Malvaceae), commonly known inEnglish as roselle or red sorrel and in Arabic as karkadeh, is widelygrown in Central and West Africa, South East Asia, and elsewhere.Depending on where it is grown, roselle is an annual or perennialherbaceous shrub and the botanical features of which have been de-scribed by Ross (2003). The thick, red and fleshy, cup-shaped calycesof the flower are consumedworldwide as a cold beverage and as a hotdrink (sour tea). These extracts are also used in folk medicine againstmany complaints that include high blood pressure, liver diseases andfever (Dalziel, 1973; Ross, 2003; Wang et al., 2000). The red anthocy-anin pigments in the calyces are used as food coloring agents (Esselen& Sammy, 1975). The swollen calyces are the part of the plant of com-mercial interest (DeCastro et al., 2004; Mottram & Puckey, 1978) asthey are rich sources of vitamin C, phytochemicals, and are alsoused as a natural food coloring. The calyxes are used to make jelliesand jams which are said to taste like an acidic plum jam. The charac-teristic red color elicited by the decoction of this plant is produced bythe anthocyanins (Guo, 1986; Wang et al., 2000), hibiscin (Gowali,1982), and to a lesser degree, by the delphinidin-3-glucoside andcyanidine-3-glucoside. The presence of β-carotene has also beenreported, as well as riboflavin, thiamine, niacin, and the ascorbic,malic and hibiscic acids (El-Merzabani, El-Aaser, Attia, El-Duweini, &Ghazal, 1979).
82 2 710 9479.
rights reserved.
Various herbal species were reported as good sources of antioxi-dants for delaying lipid oxidation in meat products (Formanek et al.,2001; McCarthy, Kerry, Kerry, Lynch, & Buckley, 2000). Most of thereported results associated functional properties of roselle with thecomposition of polyphenolic compounds and antioxidant capacity,antiaerobic effects of roselle extract in raw and frozen pork or beefpatties. This study is focused on the possibility to use roselle water ex-tract in cooked pork patties.
In recent years, the consumer demands for healthier meat and meatproductswith reduced level of fat, cholesterol, decreased contents of so-dium chloride and nitrite, improved composition of fatty acid profileand incorporated health enhancing ingredients are rapidly increasingworldwide. Fat in processed meat products contributes functional andorganoleptic characteristics, and plays an important role in the forma-tion of stable meat emulsions (Hughes, Mullen, & Troy, 1998). Fat re-placements or substitutes are ingredients that contribute a minimumof calories to formulated meats and alter flavor, tenderness, mouthfeel, viscosity and other sensory and processing properties (Cengiz &Gokoglu, 2005; Pappa, Bloukas, & Arvanitoyannis, 2000). The replace-ment of animal fat with vegetable oils in meat products has beenfound to be an efficient and successful tactic to increase the nutritionalvalue of meat foods by decreasing saturated fatty acids levels andadding natural antioxidants as roselle. Commercial precooked meatproducts may be frozen uncooked, frozen cooked, or cooked and storedat refrigerator temperature. Since precookedmeat products such as pat-ties and sausages are stored chilled or frozen, consumers use manycooking methods for reheating and eating. A major problem withmanufacturing restructured and other comminuted meat products ismaintaining the cooked color of itself. Whenmeat products are cooked,
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their color changes from red to browndue to the formation of ferro/ferrihemochrome.
Consumer interest in food containing natural ingredients has mo-tivated the food industry to evaluate the effectiveness of naturally oc-curring components of food for functional purposes other than theircommonly recognized ones.
The purpose of this study was to investigate the acceptable effectsof roselle extract on ground pork and to focus on the possibility to useroselle extract in cooked pork products. To obtain ideal combinationlevels, the importance of determining the optimum levels of these re-placements in pork patties comes into prominence. Response surfacemethodology (RSM) is an effective tool to find these optimum levelsof the processing variables for the parameters studied (Hunter,1959). Therefore, we studied the effect of processing variables suchas roselle extract (0.1–1.3%), soybean oil (5–20%) on cooking proper-ties of pork patties and to find the levels of processing variables tomaximize and minimize the cooking parameter.
2. Material and methods
2.1. Plant material and extraction
Dried roselle calyx plants were obtained from an herb maker(GDG Schuette Gmbh & Co. Kg, Germany). Dried roselle powder(20 g) were mixed with distilled water in a ratio of 1:40 (w/v), andextracted at 98 °C for 16 min and then dried in vacuum freezedryer. Extraction ratios (roselle: water) were determined based onmoisture content of dried (10%) roselle powder. No stirring was ap-plied for hot extraction. After extraction, sample was filtered usingWhatman No. 4 filter paper and was concentrated in a rotary vacuumevaporator (N-1000; Eyela, Tokyo, Japan), followed by freeze-drying(IlShin Lab Co., Ltd. Korea). Total yield of water extract was 38%.
2.2. Experimental design
Optimal roselle extract and soybean oil contents were determinedby response surface method (RSM) which was applied to the experi-mental data using a commercial statistical package, Design ExpertVersion 7 software (Stat-Ease, Inc., Minneapolis, MN, USA). Experi-mentswere randomized in order tominimize the effects of unexplainedvariability in the observed responses due to extraneous factors. Theexperimental designs involved 10 experiments with 2 replications ofthe central point in order to calculate the repeatability of the method(Montgomery, 2001). Experiments were done in triplicates. A centralcomposite design (CCD)was used to investigate the effects of two inde-pendent variables (soybean oil and roselle extract contents) on the de-pendent variables (pH, water holding capacity (WHC), cooking loss,diameter reduction (DR), thickness reduction (TR), color, texture andsensory properties). The data obtained from the CCD design was fittedwith a second order polynomial equation.
The equation was as follows:
Y ¼ β0 þX2i¼1
βiXi þX2i¼1
βiiX2i þ∑
i∑j¼iþ1
βijXiXj
where Y is the predicted response; β0 is a constant; βi is the linear co-efficient; βii is the quadratic coefficient, βij is the interaction coeffi-cient; and Xi and Xj are independent variables. The adequacy of themodel was determined by evaluating the lack of fit, coefficient of re-gression (R2) and the Fisher test value (F-value) obtained from theanalysis of variance (ANOVA). Statistical significance of the modeland model variables was determined at the 5% probability level(pb0.05). The software uses the quadratic model equation shownabove to build response surfaces. Three-dimensional response surfaceplots were generated by keeping one response variable at its optimal
level and plotting that against 19 factors (dependent variables). Theactual values of the factors for the experimental designs are given inTable 1.
2.3. Patty preparation
Lean meat from pork hams was obtained from a local market(Jungilpum, Yongsan-Gu, Seoul, Korea). All subcutaneous fat was re-moved from the muscles and the meat was boned, trimmed andground with a 3 mm grid. The spice mixture (sugar 1.3%, salt 0.7%and ground black pepper 0.1%) was added to ground pork and two in-gredients were used in various proportions (Table 1). The two inde-pendent variables were soybean oil and roselle extract contentswhich could affect quality characteristics of pork patty. Test ingredi-ents (soybean oil and roselle extract) were screened at levels rangingfrom 5 to 20 g and 0.1 to 1.3 g, respectively to determine their opti-mum working concentrations through preliminary test. Three soy-bean oil concentrations (5, 12.5, 20 g) and three roselle extracts(0.1, 0.7, and 1.3 g) were selected by central composite design(CCD). The pork patty was kneaded for 8 min by using small sizecommercial mixer (Model 5KSM150, Kitchen Aid, Michigan, USA) ata rapid speed (4 rpm) for 4 min and then at a low speed (2 rpm)for additional 4 min to homogeneous patty dough. The patty dough(100 g) was shaped into patties with 100 mm diameter and 11 mmthickness using a metal burger press (Spikomat Ltd, UK). For cookingprocedure, patties were cooked in a preheated electric oven(GO1518SP Shunde Galanz, Microwave oven Electrical ConvexKorea Application Ltd, Korea) set at 200–210 °C for 10 min. Duringcooking, core temperature of patty was monitored by water proofdigital thermometer (RT-903, China). The final internal temperaturereached over all patties was determined to change between at 70and 75 °C. After cooking, patty samples were allowed to cool to25 °C in room conditions.
2.4. Physicochemical characteristics analysis
2.4.1. Determination of pHFive gram portions of patties were mixed with 45 ml distilled
water and homogenized by Bag Mixer 400 (Interscience, France) for120 s and measured at 20 °C with pH meter (F-51, HORIBA, Tokyo,Japan).
2.4.2. Determination of water holding capacityWater holding capacity was determined according to the method
of Estelle, Kakuda, Mullen, Arnott, and de Man (1986). Yield (%) wasmeasured by weighting the product before and after centrifugation.Ten grams of samples were mixed with 40 ml distilled water intube and were incubated in water bath at 30 °C for 30 min. The mix-ture was then centrifuged at 3000 rpm for 30 min and supernatant
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was pipetted before additional incubation for 10 min and was re-moved by pipetting again. Results are expressed as percentage offluid release.
Water� holding capacity %ð Þ¼ Weight of sample after removing supernatant
Weight of sample mixed with distilled water� 100:
2.4.3. Determination of cooking lossCooking loss of the patty samples was calculated using the equa-
2.4.5. Color measurementsThe instrumental color of the meat samples were measured at
three different spots on the sample surface, using a Chroma Meter(CR-300, Minolta Co., Ltd, Osaka, Japan), calibrated to white standardplate (L⁎=97.26, a⁎=−0.07, b⁎=1.86).
2.4.6. Texture measurementAfter the patty samples were cooked and cooled to room temper-
ature, all patty samples were subjected to texture profile analysiswith three replicates using the texture analyzer (TA. XT Express v2.l,Stable Micro Systems Ltd., London, England) with the Texture ExpertProgram. Texture profile analysis procedure involved the preparationof three squares of 20 mm×20 mm×10 mm from each patty. Theoperation conditions for texture analyzer are shown in Table 2. Thetexture of sample was analyzed 3 times per replication. Text attri-butes such as hardness, adhesiveness, springiness, chewiness, gum-miness, and cohesiveness were analyzed.
Sensory evaluation was performed according to the seven pointhedonic scale. Test samples were cut into 2 cm3 cubes and served inplastic containers and coded with three-digit random code numbers.Patties were served warm and ten test samples were prepared in ran-dom order to 25 panelists. The panelists were asked to evaluate thepreference of color, flavor, tenderness, juiciness and overall qualityof patties prepared with roselle extract and soybean oil by giving ascore ranging from 1 (dislike extremely) to 7 (like extremely).
2.6. Preparation of optimized pork patty with roselle extract and soybeanoil
According to optimized roselle extract and soybean oil content,minced pork was assigned to one of the following three treatments:pork was prepared by adding roselle extract at 0.85 g of patty (HP);patty added with roselle extract was comparable with those of the0.02% BHA of patty (BP); control patty addition without roselle ex-tract (CP). Soybean oil (12.72 g) and the spice mix (sugar 1.3 g, salt0.7 g, and ground black pepper 0.1 g) were added to three treatmentsequally as described before by the same way. Patty batter wereformed into 100 g, wrapped with polyethylene film and stored at4 °C until 15 days for further analysis. On each evaluation day, threetreatment groups (HP, BP, and CP) were cooked to measure cookingproperties (cooking loss, diameter reduction, and thickness reduction),mechanical properties (color and texture), and sensory evaluation bythe same method described earlier.
2.7. Statistics analysis
Numerical optimization technique of the Design-Expert softwarewas used for simultaneous optimization of the multiple responses.The desired goals for each variable and responsewere chosen. All the in-dependents variables (roselle extract and soybean oil contents) werekept within range while the responses (sensory evaluation variables)of color, flavor, juiciness, tenderness, and overall quality which statisti-cal significance of the model and model variables were resulted at the5% probability level (Pb0.05) were kept maximum goal. Through nu-merical optimization, desirability was calculated following equationand the highest desirability was chosen (point prediction).
D ¼ d1 � d2 �…� dnð Þ1n ¼ ∏n
i−1di
� �1n
D=overall desirability, d=desirability, n=response.Graphical optimization was obtained from the overlap graph
when the minimum or maximum point for each response was input.
3. Results and discussion
3.1. pH
The pH values differed statistically (pb0.001) among the assays,and an increase in the roselle extract content resulted in a lower pHof the patty (Fig. 1), which ranged from 4.80 to 5.92. The highest pHof the patty was observed when 20 g of soybean oil and 0.1 g of ro-selle extract was used and the lowest pH was observed when 12.5 gof soybean oil and 1.3 g of roselle extract was used. The pH of pattydepended on the amount of the roselle extract added because thepH of the roselle water extract was 2.41. The results of the modelsignificance, equation and coefficients of determination of themodel equations to examine the effects of the independent variables(soybean oil and roselle extract) on pH of the patty are shown inTable 3. These results indicated that the model for pH was linear andwas highly adequate with satisfactory R2 values (0.8947) (Fig. 1). The
Fig. 1. Response surface plot of the physicochemical characteristics of the pork patties containing soybean oil (A) and the roselle (Hibiscus sabdariffa L.) extract (B).
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final pH of the muscle is very important due to the positive correlationwith WHC during the conversion of muscle to meat (Bee, Anderson,Lonergan, & Huff-Lonergan, 2007). The decrease ofmeat pH to near iso-electric point results in the decrease of WHC (Swatland, 2008).
3.2. Water holding capacity
Table 3 shows the water holding capacity of cooked pattiescontaining the roselle extract, as measured using the method described
by Estelle et al. (1986). The roselle extract and soybean oil were bothhad a significant (pb0.05) effect on theWHC of patties (Table 3). An in-crease in the roselle extract and soybean oil content resulted in a higherWHC of the patty (Fig. 2), which ranged from 8.22% to 33.99%. Themaximum and minimum WHC of the patties was when 20 g and 5 gof soybean oil and 1.3 g and 0.1 g of the roselle extract, respectively,were used. This most likely occurred because an increase in the roselleextract content increased theWHC of the patties; the roselle extract in-creased moisture retention in the matrix. However, Tekin, Saricoban,
Table 3Analysis of predicted model equation for physicochemical characteristics of pork patties prepared with soybean oil and roselle extract.
Model Mean±S.D. R2a F-value Prob>F Polynomial equationb
pH Linear 5.31±0.14 0.8947 29.74 0.0004⁎⁎⁎ 5.31−0.018A–0.44BWHC Linear 19.58±0.14 0.6474 6.43 0.0260⁎ 19.58+5.17A+6.71BCooking loss 2FI 23.77±4.23 0.5277 2.23 0.187 23.77+3.65A–0.51B–3.10ABDiameter reduction Quadratic 12.55±2.25 0.6024 1.21 0.4384 14.35−1.09A+0.99B–1.02AB–1.92A2–1.08B2
Thickness reduction Linear 10.49±4.12 0.6996 8.15 0.0149⁎ 10.49+6.43A–2.19BL Linear 54.17±2.20 0.9176 38.97 0.0002⁎⁎⁎ 54.17−0.18A–7.94Ba Linear 6.23±0.32 0.9815 185.76 0.0001⁎⁎⁎ 6.23−0.003A+2.54Bb Linear 6.91±1.82 0.8200 15.94 0.0025⁎⁎ 6.91+0.065A–4.19B
a 0bR2b1, close to 1 means more significant.b A: soybean oil, B: roselle extract.⁎ pb0.05.
⁎⁎ pb0.01.⁎⁎⁎ pb0.001.
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and Yilmaz (2010) reported that at higher salt concentration, the pro-tein denaturized, unfolded and exposure of the hydrophobic area ofthe proteins increased, leading to aggregation and loss of water fromthemuscle. Cross-linking between proteins and shrinkage of themusclemight have resulted in an increase in the space for water and thereforeincreased theWHC (Thorarinsdottir, Arason, Bogason, & Kristbergsson,2004). Based on these report, the protein in the patty samplesmay haveswelled more due to the higher WHC if processed at an initially lowersalt concentration.
Fig. 2. Response surface plot of the texture characteristics of the pork patties co
3.3. Cooking loss
The effect of soybean oil and roselle extract on the cooking loss ofpatties is shown in Table 3. Soybean oil was the independent variable,which had a 2FI (two factor interaction) model on cooking loss andwas not significant (p>0.05). The cooking loss was found to dependon the amount of soybean oil added, since an increase in the cookingloss of patties and roselle extract did not alter (p>0.05) the cookingloss in the 2FI model. This result was similar to those reported by
ntaining soybean oil (A) and the roselle (Hibiscus sabdariffa L.) extract (B).
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Yin and Chao (2008), where the addition of the roselle calyx extractsor protocatechuic acid was shown to not affect the cooking loss ofbeef patties. In addition, Tekin et al. (2010) reported that the cookingyield, moisture, fat retention and reduction in thickness values de-creased as the amount of fat increased. It was reported that themean free distance between fat droplets decreased as the fat contentincreased, which causes fat coalesces and fat leakage from the prod-uct (Tornberg, Olsson, & Person, 1989). Therefore, this might be at-tributed to excessive fat separation and water release in the higherfat including meatballs during cooking. A similar trend in cookingloss was reported by Koo et al. (2009). They reported that the cookingloss of beef patties containing various plant oils tended to decreasedwhen compared to beef patties not containing plant oils (pb0.05),and the cooking loss of olive oil and sunflower oil treated pattieswas lower than that of canola oil and corn oil treated patties.Whiting (1987) also founded that a high polyunsaturated fatty acidcontent in sausage resulted in a decrease in the loss of water and fat.
3.4. Diameter reduction
In this analysis, soybean oil was the independent variable, whichwas fit to a quadratic model, and the differences were not significant(Table 3, p>0.05). The presence of fat decreased the reduction inpatty thickness; however, it increased the reduction in patty diame-ter. This result was consistent with the findings of Serdaroglu andDegirmencioglu (2004), who determined that meatballs formulatedwith 20% fat had a higher reduction in diameter. Thus, the additionof the extract resulted in an increase in the reduction in diameter ofpatties but this difference was not significant (p>0.05).
3.5. Thickness reduction
Table 3 shows that the soybean oil and roselle extract had a signif-icant (pb0.05) effect on thickness reduction. Fig. 1 shows that soy-bean oil increased and roselle extract decreased the rate ofreduction in the thickness of patties. During the cooking process,patty samples shrunk because of the denaturation of meat proteinsby heat and acid. This resulted in a loss of water and fat, which furthercontributed to the reduction in the shrinkage process. Serdaroglu andDegirmencioglu (2004) also found that the fat level affected meatballshrinkage, where a decrease in the fat level from 20% to 5% resulted ina decrease in the shrinkage of patties
3.6. Color
TheCIE system,which included L⁎ (lightness), a⁎ (redness/greenness)and b⁎ (yellowness/blueness) values, has been shown to be closely as-sociated with sensory perception (Salces, Guyot, & Herrero, 2005).The soybean oil and roselle significantly increased the L⁎ values of pat-ties (Table 3) and this effect was shown to be concentration dependent,where the L⁎ values of the patty ranged from 46.28 to 65.44. The max-imum and minimum L⁎ values of patties were observed when 20 g ofsoybean oil and 0.1 g and 1.3 g of the roselle extract, respectively,were used. The redness depended on the amount of the roselle extractadded, which increased linearly with an increase in soybean oil androselle concentration (pb0.001). The b⁎ values differed statistically(pb0.01) and an increase in the roselle extract content resulted inlower b⁎ values, which ranged from 3.27 to 13.60. Thus, an increase inthe roselle extract content resulted in a decrease in the lightness ofmainly determined by the presence of denatured-globin hemochromes,which are formed as a result of high temperatures, colored Maillardproducts upon heating, the physicochemical state of proteins andother meat components (Lawrie, 1998). Thus, the color changes duringheatingweremost likely associatedwith the formation ofMaillard reac-tion products (MRP). MRP were reported to be responsible for colorchanges; however, color differences were not correlated with heating
time (Morales & Jimenez-Perez, 2000). The partial replacement ofpork back fat with vegetable oils led to a significant modification ofthe color measured on the surface of the cooked patties. Patties treatedwith vegetable oils showed significantly higher L⁎ values.
3.7. Texture
Instrumental texture profile analysis was carried out on thecooked pork patty and texture attributes, such as hardness, adhesive-ness, springiness, chewiness and gumminess were selected as the re-sponse variables. Table 4 shows the effects of added soybean oil androselle extract levels on the textural properties of cooked pork patties.None of the samples exhibited significantly different springiness andcohesiveness values. The hardness of pork patties were also shown todepended on the amount of the roselle extract and soybean oil added,which decreased linearly with an increase in treatment concentration(pb0.01). The model for hardness was linear and with a satisfactoryR2 value (0.749). An increase in the roselle extract content wasshown to result in a decrease in the hardness of the patty and theroselle extract had a greater effect on the hardness of cooked porkpatties than the soybean oil. Different results were reported by Ulu(2006) in both raw and cooked meatballs. In addition, Cofrades,Carballo, and Colmenero (1997) founded that high-fat frankfurterswere harder than low-fat frankfurters. This difference might be at-tributed to the composition and characteristics of the fat, which hada strong impact on the textural properties of meat products (Lawrie,1998). Soybean oil and the roselle extract both had an effect on adhe-siveness, which occurred through a two factor interaction effect(Table 4, pb0.05). Soybean oil caused a decrease in the adhesivenessof patties. This was consistent with the results of Ulu (2006), whoreported that fat gave rise to a decrease in the adhesiveness of thepatties. To produce high quality patties, its adhesive properties shouldbe reduced by increasing the fat content. Springiness is a measure ofhowwell a product physically springs back after it has been deformedduring the first compression (Texture Technologies, 2003). Springi-ness values are related to the elastic properties of the patty, where adecrease in the springiness value indicates that the elasticity of thepatty decreased. Ulu (2006) founded that springiness increased inboth raw and cooked meatballs when the fat level was decreased.This result was also in agreement with that of Crehan, Hughes, Troy,and Buckley (2000) who reported that fat reduction from 30% to12% or 5% result in an increase in springiness. Chewiness was calculatedusing hardness as a factor, which measures the resistance to compres-sion force. The linear effect of the roselle extract on chewiness was neg-ative as seen by its effect on hardness (Table 4). In the ridge analysis, theminimum chewiness (1157.71 N×mm) and maximum chewiness(3090.53 N×mm) was observed when 20 g and 12.5 g of soybean oiland 1.3 g and 0.1 g of roselle extract, respectively, were used.
Similar results were reported by Rodríguez-Carpena, Morcuende,and Estévez (2012). In this previous study, avocado oil was determinedto have the largest effect on the texture parameters of cooked burgerpatties of all oils tested. Patties containing avocado oil had significantlylower chewiness and gumminess values (pb0.05). Soybean oil and theroselle extract had significant effects (pb0.05) on the gumminess ofcooked patties. Soybean oil and the roselle extract both decreasedthe gumminess of patties. The minimum (1674.92 N) and maximumchewiness (3748.46 N) occurred when 20.0 g and 12.5 g of soybeanoil and 1.3 g and 0.1 g of the roselle extract, respectively, were added.Cohesiveness is a measure of how good the sample retains its structureafter compression (Texture Technologies, 2003). Similar to the springi-ness, the two factors decreased the cohesiveness (Table 4) butthis decrease was not significant (p>0.05). In the ridge analysis, theminimum (0.45) and maximum (0.64) cohesiveness were observedwhen 20.0 g and 12.5 g of soybean oil and 1.3 g and 0.1 g of roselle ex-tract, respectively, were used.
Table 4Analysis of predicted model equation for the texture characteristics and sensory test of patties prepared with soybean oil and roselle extract.
Response Model Mean±S.D. R2a F-value Prob>F Polynomial equationb
a 0≦R2≦1, close to 1 means more significant.b A: soybean oil, B: roselle extract.⁎ pb0.05.
⁎⁎ pb0.01.
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3.8. Sensory properties
The regression models for color, juiciness, tenderness and overallquality were significant (pb0.05). Color preference of patties wasaffected by the amount of roselle used, with positive linear and nega-tive quadratic effects at pb0.01. Flavor was low initially and graduallyincreased as the amount of added soybean oil and roselle was in-creased but this increase was not significant (Table 4, p>0.05). Boththe soybean oil and roselle extract had similar effect on the juiciness.The juiciness was significantly affected by the amount of soybean oiland roselle used, with positive linear and negative quadratic effectsat pb0.05. These results indicated that the model for juiciness scorewas highly adequate with a satisfactory R2 value (0.9382). The prefer-ence of tenderness was significantly increased to moderate levels athigher roselle concentrations, and linear and quadratic effects of theroselle on tenderness were positive and negative, respectively, andthe effect was curvilinear, due to a significant interaction term(Table 4). The decreased in hardness after soybean oil addition inthe TPA (texture profile analysis), was also perceived by the panelswho scored the tenderness. The regression model showed that theaddition of soybean oil and the roselle extract had negative linearand negative quadratic effects and positive linear and negative qua-dratic effects on the overall quality, respectively. The maximum over-all quality score (5.42) was observed when 12.50 g of soybean oil and0.7 g of the roselle extract was added (Fig. 3). Therefore, it could beconcluded that patties enriched with b0.85% roselle extract werefound to be more suitable with respect to overall quality. Pappa etal. (2000) reported both the replacement of olive oil for porkback-fat and the pectin level significantly affected (pb0.05) the over-all acceptability of the low-fat frankfurters. A negative correlation wasfound between these two ingredients and overall acceptability. Tex-ture is the most important factor in deciding the overall acceptanceof patty products. Thus, determining the optimum levels of texturalparameters based on the maximum sensory score is necessary whenexamining the effects of processing variables on the chemical andtexture profile analysis (TPA) parameters, cooking properties andsensory properties. Therefore, the results obtained in this studywould be useful to the meat industry, which tends to replace the fatand antioxidants in patties to a level as optimal as possible, whilemaintaining a satisfactory eating quality.
3.9. Optimization of pork patty
In this study, optimization was applied within the experimentalsoybean oil and roselle extract concentrations in order to determinethe optimum formulation for patties. Using the numerical optimiza-tion technique in the Design Expert software, optimum levels of soy-bean oil and roselle extract for functional patties were determined by
superimposing the contour plots of all the responses (physicochemical,texture parameters and sensory properties). A series of contour plots(nineteen of each response) were generated and compared visually.
The contour plots were superimposed (Capanzana & Buckle, 1997),and an area of optimum performance was located for all the responsevariables in which the limits of each response were established. The re-gion that satisfied all the limits was selected as the optimum point. Byanalyzing the contour plots and evaluating the relationships betweenresponse and variables, an optimum formulation for the patty, whichhad amoderatewater holding capacity, cooking loss, reduction in diam-eter and thickness, texture, moderate sensory scores on color, flavor,juiciness, tenderness and highly accepted by panels, was presented.Based on these superimposed plots, it was suggested that the optimumformulation of the roselle patty was 12.72 g of soybean oil and 0.85 g ofthe roselle extract and the predicted values for each of response vari-ables were as follows; pH — 5.20, cooking loss — 23.73%, diameterreduction — 14.49%, thickness reduction — 10.14%, water holdingcapacity — 121.38%, L* — 52.22, a* — 6.85, b* — 5.88, hardness —
4606.71 N, adhesiveness — −2.71 g×s, springiness — 0.79 mm,chewiness — 2140.46 N×mm, gumminess— 2664.63 N, and cohesive-ness — 0.57. In addition, the sensory scores for color, flavor, juiciness,tenderness and overall quality were 5.34, 4.68, 5.06, 5.30 and 5.26, re-spectively (Fig. 4).
The desirability function approach is one of the most widely usedmethods for the optimization of the multiple response process. Desir-ability concept for multi‐criteria optimization in industrial qualitymanagement was introduced by Harrington (1965). It is based onthe idea that the quality of a product or process that has multiplequality characteristics is unacceptable when one of them stays out-side of some desired range. The method finds operating conditionsthat provide the most desirable response values (Shi et al., 2008).
3.10. Physicochemical characteristics of optimized pork patty with thesoybean oil and roselle extract
Thephysicochemical characteristics of optimized roselle (H. sabdariffaL.) patty (HP), 0.02% BHA added patty (BP), and control patty (no addedantioxidant, CP) are shown in Table 5.
3.10.1. pHThe pH of HPwas the lower (5.66) than BP (6.32) and CP (6.36) and
this differencewas significant (Table 5, pb0.001). This resultmost likelyoccurred because the pH of the acidic roselle extract was 2.41.
3.10.2. Water holding capacityHP had the highest water holding capacity relative to the other
patty groups and no difference was observed between BP and CP(pb0.01). The water holding capacity is a measure of the ability to
Fig. 3. Response surface plot of the sensory characteristics of the pork patties containing soybean oil (A) and the roselle (Hibiscus sabdariffa L.) extract (B).
Fig. 4. Response surface plot of the desirability and overlay plot of optimized the pork patties containing soybean oil (A) and the roselle (Hibiscus sabdariffa L.) extract (B).
398 E. Jung, N. Joo / Meat Science 94 (2013) 391–401
A HP, roselle (Hibiscus sabdariffa) extract added patty; BP, 0.02% butylatedhydroxyanisole added patty; CP, no antioxidant added patty.
B a, b, c means in a row followed by different superscripts are significantly different(pb0.05) by Duncan's multiple range test.
⁎ pb0.05.⁎⁎ pb0.01.
⁎⁎⁎ pb0.001.
399E. Jung, N. Joo / Meat Science 94 (2013) 391–401
holdwater thatwas added or containedwithin themeat, when physicalforces such as cutting, comminution, compression, heating etc.were ap-plied to themeat. It is affected directly by the structure characteristics ofthe proteins in meat and is an important factor impacting sensory char-acteristics and economic properties (VanOeckel, Warnants, & Boucqué,1999). Wu and Smith (1987) reported that the water holding capacityincreased when the protein structure and strength of ions werechanged. It is also possible that the acidic roselle extract changed theprotein structure.
3.10.3. Cooking lossCooking loss of three groups was significantly different (pb0.01).
HP was 17.45% and was lower than (26.06%) and CP (21.34%).
3.10.4. Diameter reductionThe reduction in diameter of the three groups was not significantly
different (p>0.05). CP had the highest reduction in diameter (13.03%).
3.10.5. Thickness reductionReduction in thickness of HP was the lowest in the three groups
(9.61%) and significant differences were observed (pb0.05). Changesin the thickness reduction were similar to the changes in cooking loss.
Table 6Texture and sensory properties of the pork patty containing the optimized amount of the s
A HP, roselle (Hibiscus sabdariffa) extract added patty; BP, 0.02% butylated hydroxyanisoB a, b, c means in a row followed by different superscripts are significantly different (pb⁎ pb0.05.
⁎⁎ pb0.01.⁎⁎⁎ pb0.001.
Generally during the cooking process, beef patty proteins becomedena-tured by heat and, consequently, there is a loss of water. Fat has alsobeen shown to contribute to the shrinkage process (Tekin et al.,2010). Shrinkage is a process inwhich some loss ofwater and fat occurs.
3.10.6. ColorThe effect of the optimum roselle extract concentration on the
Hunter L⁎ a⁎ b⁎ values of patties manufactured from pork is presentedin Table 5. The optimized patty with roselle (HP) led to a significantmodification of the color (L⁎, a⁎, and b⁎) measured on the surface ofthe cooked patties. The lightness value of HP (56.08±1.20) was lowerthan that of BP (68.38±1.16) and CP (66.92±0.81) (pb0.001). HPhad the lowest yellowness (4.27±0.48) and this difference was signif-icant (pb0.001). HP also had a higher redness value (6.25±0.72) thanBP (3.77±0.14) and CP (4.06±0.09) (pb0.01). The roselle extract wasidentified as being effective in terms of meat redness, since addition ofthis extract resulted in a significantly (pb0.05) higher Hunter a⁎ valuesthan the control and BHA added patty.
Renerre and Labadie (1993) suggested that upon exposure to air,myoglobin combines with oxygen to form bright red oxymyoglobin(MbO2), which is synonymous with freshness “bloom” and consid-ered attractive by the consumer. Color changes during heating wereassociated with the formation of Maillard reaction products (MRP).MRP were reported to be responsible for color; however, color differ-ences did not correlate with heating time (Morales & Jimenez-Perez,2000). It is likely that the roselle cold water extract contains glycosidecompounds, in which one or more of the phenolic hydroxyl groupswere bound to a sugar moiety through a hemiacetal bond. Heatingmay break such bonds by releasing free sugars, which in their ownturn were able to participate in various interactions, resulting in theformation of new compounds, e.g. MRP, which influence the color.In later reaction stages, MRP and/or sugars may participate in the for-mation of new polyphenolic compounds and some of themmay scav-enge DPPH radicals by increasing the total radical inhibition in thecase of the heated extract.
3.11. Texture characteristics of optimized pork patty with the soybean oiland roselle extract
The effect of the roselle extract on the texture of cooked pork pattyis presented in Table 6. All other characteristics of instrumental tex-ture profile except adhesiveness were significantly different betweenHP, BP and CP (pb0.05). The hardness, chewiness and gumminess of
oybean oil and roselle extract.A
CPB F-value
548.81a 6247.72±203.28b 136.94⁎⁎⁎
0.82 −1.00±0.83 1.83
0.01ab 0.87±0.03b 3.98⁎
230.68a 3661.62±451.84b 84.73⁎⁎⁎
292.75a 4181.40±452.33b 92.91⁎⁎⁎
0.02ab 0.67±0.07b 7.31⁎⁎
1.25b 4.04±1.16b 5.47⁎⁎
1.39b 4.04±1.16b 3.87⁎
1.38b 5.04±1.52a 5.63⁎⁎
1.38b 4.88±1.60a 5.37⁎⁎
1.33b 4.62±1.41ab 3.84⁎
le added patty; CP, no antioxidant added patty.0.05) by Duncan's multiple range test.
400 E. Jung, N. Joo / Meat Science 94 (2013) 391–401
HP and BP were similar but different when compared to CP, and thespringiness and cohesiveness of HP were lower than the other twotreatment groups. It can be observed that the hardness value of HP(3427.76±103.16) was lower than that of CP (6247.72±203.28), andthe effect of the roselle extract and BHA on hardness was not different.The springiness of HP (0.83±0.03) was the most inflexible, and that ofCP was the highest; the roselle extract had a negative effect on springi-ness. HP had a higher chewiness (1613.37±94.18) and gumminess(1936.20±83.63) than BP but these values were lower than those ob-served for CP. The roselle extract had a negative effect on the chewinessand gumminess. Similar to the springiness, the cohesiveness of HP(0.57±0.02) was the lowest. Thus, the roselle extract significantly de-creased the cohesiveness of patties (pb0.01).
3.12. Sensory properties of optimized pork patty with the soybean oil androselle extract
Panel testing was conducted to evaluate the acceptability of thepatties containing the roselle extract additives. The results of thisanalysis are presented in Table 6. A comparison of the treatmentsshowed that there were significant differences (pb0.05) betweenthe samples without additives (CP) and the samples with the roselle(H. sabdariffa) extract (HP) as well as between the samples withBHA (BP) and the samples with the roselle extract (HP). In general,there was a higher preference for samples containing the roselle ex-tract in all quality attributes tested, including color, flavor, juiciness,tenderness and overall quality, than the control group. It is quite evi-dent that cooked pork patties containing the optimum roselle extractcontent had superior sensory characteristics.
4. Conclusions
RSM was successfully used to identify the best combination of soy-bean oil and roselle extract to create a low fat-functional patty and toobtain an innovative functional pork patty with a high sensory accep-tance and suitable physicochemical properties. The results obtained inthis study will be useful to the meat industry, which tends to decreasethe saturated fatty acid content with a concomitant enrichment in theunsaturated fatty acids content. The roselle content added to the porkpatties were kept as low as possible, while maintaining satisfactory eat-ing quality. The amount of roselle extract to be added to a pork patty forindustrial applications should be slightly less than the highest concen-tration (0.85 g/100 g). This was the case because the color as well astheflavor of the patties treatedwith the highest concentration of the ro-selle extract scored a slightly lower favorably rating. Nevertheless, theadvantage of the roselle extractwas the pleasant color of themeat prod-uct. In addition, the flavor of the cooked pork patties was maintained,which was not the case when spice extracts, such as rosemary and gar-lic, were used. The use of plant extracts in meat may alter the productsensory characteristics, particularly flavor and color. Undesirablechanges in flavor and color can have a negative effect onmeat productsprepared with other plant extracts. And further research is necessary toexamine the lipid oxidation stability of pork patty and antimicrobial ac-tivity of during storage period.
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